Heat exchanger



' JulyY 12, 1949.

Filed Jan'. e, 1944 Lf McT. CAMERQN I5 Sheets-Sheet l @Mm www July-l2, 1949. L. MCT. cAlvuRoNy 2,476,179 v HEAT EXCHANGER- Filed Jan. 6, 1944 l 3 Sheets-Sheet 2 July12,1`949. L, McTpAMl-:RON 2,476,179

HEAT EXCHANGER Filed Jan. e, 1944 s sheets-sheet s Patented July l2, 1949 HEAT EXCHANGER Lachlan McTavish Cameron, Bristol, England, assignor to The Bristol .Aeroplane Company Limited, Bristol, England, a British company Application January 6, 1944, Serial No. 517,271 I n Great Britain August 12, 1942 section 1, Public Law 69o, August s, 194s Patent expires August 12, 1962 4Cla1ms. (Cl. 257-235) This invention concerns improvements in or relating to heat-exchangers and has for its object to provide a construction of heat-exchanger in which one of the two fluids passing therethrough is enabled to enter and leave the heat-exchanger in a number of different directions.

To this end a heat-exchanger in accordance 4 with the present invention comprises a plurality, for example. two, heat-exchange compartments which are disposed side-by-side and ducts leading fluid to' and from said compartments, the arrangement being that one of the two fluids passing 2 f minimum the various components are placed as far as practicable one behind the other. Thus the air-compressor (which is constituted by an axial-flow compressor 6 in series with a centrifugal compressor 1) is disposed at the front of the unit, i. e. facing the direction of motion of the aircraft, the turbine unit which is generally indithrough the heat-exchanger is ldivided into two streams one for each compartment, the streams passing through the compartments in dissimilar directions.

According to another feature of the invention each compartment is divided into a plurality ofv heat-exchange cells and one of said fluids ls'.

adapted to be divided into as many currents as 4 there are cells, the arrangement being that 'for each compartment, the currents pass through adjacent cells in opposite directio i Preferably the cells of one compartment are normal to the cells oi' the adjacent compartment so that` the paths followed bythe currents passing through the compartments are mutually at right angles. v

Whilst the invention is concerned with .heat- Aexchangers in general, the heat-exchanger in accordance with the present invention is particularly suitable for use in conjunction with jetpropulsion and gas-turbine units for aircraft. Accordingly two embodiments of the present inf vention as applied to a gas-turbine unit will now be described with reference to the accompanying drawings in which:

Figure 1 is a longitudinal elevation partly in section of a gas-turbine unit for an aircraft in which a heat-exchanger in accordance with the present invention is incorporated as one of the members of the unit,

Figure 2 is a section on the line 2-2of Figure 1,

Figure 3 is a view in the direction of arrow 3 of Figure 1.

Figures 4 and 5 are views respectively corresponding to Figures 2 and 3 and showing a construction of heat-exchanger for use with a gasturbine unit in which the power is transmitted to a pusher airscrew by a shaft passing through the heat-exchanger, and

Figure 6 is an explanatory diagram.

The general disposition of the elements of the gas-turbine unit, which is intended to drive a tractor airscrew, is as shown in Figure 1. To reduce the overall diameter of the unit to a cated at 8, is placed behind the compressor. the

heat-:exchanger 9 is placed behind the turbine unit and finally the discharge nozzle I0 is placed behind the heat-exchanger. The diametral dimension of the heat-exchanger 9 and turbine unit '8,is less than that yof the'centrifugal compressor l and the advantage is taken of this to placeducts II, I2 outside these componentswithout their extending materially beyond the periphery` of the compressor in a radial direction. Av

trunk I3 extends from thev discharge side of the turbine-unit to the heat-exchanger and is adapted to convey the exhaustv gases from the former to the latter. The ducts II (Figure 2) are provided to convey air from the compressor to the heatexchanger and the ductsv I2 to conveyv the preheated air from the exchanger to the turbine unit 8. The turbine unit describedoperates as folv lows:

' The compressorsl 6, 1 which are driven by the ,turbine I5 supply air to an annular expansion chamber I6.v This air is led by the cold-air ducts VII to the heat-exchanger 9 which it traverses and is then led back bythe pre-heated-air-ducts I2 to the'turbine unit 8. Disposed within each preheated-air duct is a combustion chamber Il in which the fuel is burnt vand through which the 1 whole or a part of the pre-heated air passes. The

combustion products perform work in passing through the turbine unit 8, of which the turbine I5 is coupled to and drives the compressor 6, 1 whilst the turbine I1 is coupled to and drives the airscrew, illustrated as contra-rotating co-axial airscrews. The exhaust gases from the turbine Aunit B flow along the exhaust gas trunk I3 and v through the exchanger 9 to the discharge nozzle The exhaust gases in flowing through the exchanger give up part of their heat-content to the cold air circulating therethrough so that the latter -is preheated before it approaches the com# bustion chambers.' fv

In the particularapplicatlon of the invention referred to two factors are of special importance. Firstly the pressure .drop entailed across the "cold side of thee'xchanger -is of relatively little importance whilst the vpressure drop encountered in the "hotv side is material. 'Ihe latter pressure drop must therefore-be kept at a minimum. To

3 this end, the exhaust gases from the turbine are constrained to follow a straight path to the discharge nozzle; however, the air passing from the compressor to the exchanger and thence to the turbine may Vwithout undue ill effect follow a circuitous path.

The second factor is that of ensuring uniformity of distribution by the compressor and of supply to the turbine. This requires that as great a number of outlets be spaced around the expansion chamber of the compressor as is practicable, and that a similar disposition of inlets to the turbine be provided. The construction of the heat-exchanger is such that a plurality of spaced outlets and inlets can be provided, and this is diagrammatically illustrated in Figure 6. For the sake of clarity the annular expansion chamber i6 of the compressor is shown as of rectangular form, and the inlet chamber 2| to the turbine nozzles is also shown as of rectangular form. The heatexchanger comprises two compartments I8, I9 which, also for clarity, are spaced apart andthe compartment I8 is constructed as four separate cells I8|, |82, |83 and |84, these cells extending horizontally across the compartment. Similarly, the compartment I9 is made in four separate cells I 9|, |92, |93 and |94, but these extend vertically Y across the compartment.

The hot products of combustion ow through the central openings of the parts |6 and 2| by a straight course through the compartment I9 and then through the compartment I8 so as to have as little restriction as possible to the flow. The air from the expansion chamber I6 passes by a number of tubes II to the: heat-exchanger, and two of such tubes are shown passing respectively from the top, bottom and two side sections of I6 representing a uniform distribution from the chamber I6. The two tubes II from the top horizontal section enter the cells I9| and |93 respectively, and the air passes downwards throughthese cells and then returns by the tubes I2'to the bottom horizontal 'section of the turbine inlet chamber 2|. Similarly air from the bottom horizontal section of the chamber I6 enters the cells I92'and |94 and passes upwards therethrough returning by the -tubes I2 to the top horizontal section of the chamber 2|. All the air passing through the compartment I9 travels in a vertical direction, being upwards and downwards respectively in adjacent cells.

A similar arrangement is provided for the sides of the chambers I6 and 2|, and in this case the air passes through the compartment I8. From nately towardsk the right and towards the left in adjacent cells. It will be seen, therefore, that a uniform distribution'of air from the chamber I6 is obtained by the pipes II with a uniformly distributed supply by the pipes. I2 to the chamber 2| and this uniform distribution is associated with an arrangement of cells which provides oppositely directed currents of air in adjacent cells, whilst the streams of air in the two compartments I8 and i9 respectively are mutually at right` 4 angles to one another; this arrangement provides for the highest efficiency of heat transfer.

In practice, the chambers |6 and 2| will usually be of circular i'orm as shown in Figures 2 and 3, and the heat-exchanger 8 is a cubiform structure built in normal manner from a multitude of heat-exchanger elements contained within a frame.

'I'he exchanger is mounted behind the exhaust `gas conduit with one face of the exchanger directed toward the turbine so that the gases approach normally to one face of the exchanger, pass through the exchanger and leave the opposite face thereof. In this way the exhaust gases may be discharged from around the whole of the periphery of the gas turbine and follow a comparatively free path to the discharge nozzle. The cold air side of the heat-exchanger is divided equally into two compartments I8, I9 (see Figure l) and each such compartment is further subdivided into a plurality of cells zo which extend across the compartments. The cells in the compartments IBand I9 are respectively disposed so that the cold air will travel through the compartment I8 in a horizontal direction as shown in Figure 3, whilst the cold air will travel through the cells of the compartment I 9 in a vertical direction i. e. the air in adjacent compartments follows paths which are mutually at right angles.

The flow of air and gases through the chambers is as follows:

Cold air is led by ducts II from a plurality of outlets which are equally spaced around the periphery of the expansion chamber I6 of the compressor. The number of outlets.. corresponds to the total number of cells contained in both compartments. In the embodiment shown in Figure 3 there are a total of four cells for each of the two compartments. so that the total number of cells and thus the total number of outlets from the compressor is 8.

For compartment I8 the air from the compressor is led into a cell 2|) flows across it in a horizontal direction as seen in Figure 3 and inso 45 doing gains heat from the exhaust gases which are passing successively through the two compartments I8, I9. The pre-heated air leaves the cell by the opposite face from which it entered and passes to a pre-heated air duct I2 and com- 80 bustion chamber Il and thence to one of the gas turbine nozzles 2| which are equal in number to the outlets from the compressor. The air in the next adjacent cell of the compartment t8 follows a similar path except that it iiows through the cell in an opposite direction from that for the cell already referred to. Thus the air in the bottom cell of the compartment I8 (see Figure'B) ows from left to right whilst the air in the next adjacent cell from right to left. Similarly with' the i'low of air through the other cells.

The now of air through the compartment I9 is similar to that described for compartment I8, in this case however, the air flows through the cells and 'crosses the compartment in a vertical 05 direction. -I-llere again air in adjacent cells ows in opposite directions. For instance, in the righthand cell shown in Figure 3 the ow of air is from .the bottom towards the top whereas in the next adjacent cell it is from the top towards the bottom.

It will be noted from Figures 2 and 3rthat the cold air ducts and pre-heatedair ducts I2 (which are grouped around the periphery of the exchanger 9, exhaust-gas trunk I3 and turbine 78 unit 8) are intercalated.

y the unit. This necessitates that the airscrewshaft passes from the turbine I'I through the heat-exchanger 9 and discharge nozzle IIJ. To meet the requirements of this construction the heat-exchanger has been modified as shown in Figures 4 and 5, in which like parts as are shownI in Figures 2 and 3 are indicated by the same numerals.

Thus cells 20a which are located around the outer surface of the heat-exchanger 9 convey the air from its associated cold air ducts II to their associated preheated air ducts I2 without interruption. Passing through those Acells 20h which are located at the middle of the heat-exchanger is the airscrew shaft Il. In order to maintain continuity of flow through the cells the shaft 3| is enveloped by a collector 22 which extends for the length of the heat-exchanger. The cold air moving through the cells 20h then discharges into' for conveying a second heat-exchange iiuid once,

only across the duct along straight parallel paths, the paths traversed by the second fluid along one matrix being normal to the paths traversed by said fluid through the other matrix, a plurality of inlet ducts to convey the second fluid to each matrix, a plurality of ducts to convey the second fluid from each matrix, said inlet and outlet ducts being disposed wholly around the rst fluid duct and the inlet ducts being intercalated with the outlet ducts.

3. A heat exchanger comprising a straight duct of rectangular cross-section for conveying a rst heat-exchange uid, a plurality of straight parallel tubes extending across one pair of opposite sides of the rectangular duct and forming a rst matrix to convey a part of a second heat-exchange fluid through the exchanger once only, a

It will be appreciated that the matrix of the Y .uid is admitted to the heat exchanger and an outlet duct for each cell by which fluid is discharged from the heat exchanger after having passed through one cell only, said inlet and outlet ducts being Intercalated around the periphery of the heat exchanger.

2. A heat exchanger comprising a duct for conveyinga first heat-exchange fluid, a pair of matrices lying side by side within the duct each plurality of straight parallel tubes extending across the other pair of opposite sides of the rectangular duct and forming a second matrix to convey the remainder of sid second heat-exchange uid through the exchanger once only, said matrices lying side by side, a plurality of inlet ducts for each matrix, and a plurality of outlet ducts for each matrix, said inlet and oulet ducts being spaced Wholly around the rectangular duct and being intercalated.

4. A heat exchanger according to claim 1 wherein a collector extends lengthwise of the heat exchanger through certain of the cells of both compartments and the passages of said cells communicate with said collector so that the fluid in travelling from an inlet to an outlet through said cells passes through the collector.

LACHLAN McTAVISH CAMERON.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 849,878 Zivi Apr. 9, 1907 1,067,689 Spotts July 15, 1913 1,846,067 Sadtler Feb. 23, 1932 2,162,956 Lysholm June 20, 1939 f FOREIGN PATENTS Number Country Date 69,262 Germany June 13, 1893 59,485 Sweden Mar. 5, 1924 78,993 Switzerland Feb. 17, 1919 

